1. Field of the Invention
The present invention relates to a laminated metal plate for a drawn can, and a drawn can prepared therefrom. More particularly, the present invention relates to a laminated metal plate for a drawn can, which has excellent workability and corrosion resistance and in which cracking or formation of pinholes is prevented, and a drawn can prepared therefrom.
2. Description of the Related Art
A conventional side seamless can is prepared according to the process comprising subjecting a base metal such as an aluminium plate, a tinplate or a tinfree steel plate to drawing of at least one stage between a drawing die and a punch to form a cup comprising a side seamless wall and a bottom connected seamlessly and integrally to the wall, and, if desired, ironing the wall between an ironing punch and a die to reduce the thickness of the vessel wall. Furthermore, there is known the process in which the thickness of the side wall portion is reduced by bending and elongating by a curvature corner portion of a redrawing die instead of the above-mentioned ironing (see Japanese Examined Patent Publication No. 56-501442).
As the process for forming an organic coating on side seamless can, there are known an ordinarily widely adopted process in which a formed can is coated with an organic coating, and a process in which a resin film is laminated on a base metal before the drawing. For example, Japanese Examined Patent Publication No. 59 -34580 discloses a process in which a film of a polyester derived from terephthalic acid and tetramethylene glycol is laminated on a base metal. It also is known that a metal plate coated with a vinyl-organosol, epoxy resin, phenolic resin, polyester or acrylic resin is used for producing a redrawn can be bending and elongating.
When an organic coating is formed on a base metal in advance, the coating is readily damaged by a tool at the drawing step, and at the damaged part of the coating, actual or latent exposure of the metal is caused and dissolution or corrosion of the metal is caused from this damaged part. In the production of a seamless can, such a plastic flow is brought about that the height increases in the height direction of the can but the diameter decreases in the circumferential direction of the can. By this plastic flow, the adhesion force between the metal surface and organic coating is reduced, and also the adhesion force tends to decrease with the lapse of time because of the residual strain in the organic coating or the like. This tendency is especially conspicuous when a content to be packed in a can is hot-filled or a content-filled can is heat-sterilized at a low or high temperature.